<!DOCTYPE html>
<html>
<head>
	<title></title>
</head>
<body>
    <canvas id="canvas" width="500" height="500" style="border:1px solid #000"></canvas>

</body>
</html>

<script type="text/javascript">
	var canvas = document.getElementById('canvas');
	var context = canvas.getContext('2d');
	context.fillStyle ='#eeeeef';
	context.fillRect(0,0,500,500);

	for (var i = 0; i <= 10; i++) {
		context.beginPath();
		context.arc(25*i,25*i,10*i,0,Math.PI*2,true);
		context.fillStyle ='rgba(255,0,0,0.25)';
		context.fill();
		context.closePath()
	}



	</script>